Temperature regulation of tracer valves



arch 19, W8, P. J. WEAVER 3,373,301

TEMPERATURE REGULATION OF TRACER VALVES Filed Dec. 10, 1965 INVENTOR. 7PAUL u. WEN 142 Arromvzys.

United States Patent 3,373,801 TEMPERATURE REGULATION OF TRACER VALVESPaul J. Weaver, Pasadena, Calif., assignor to True- Trace Corporation,El Monte, Califl, a corporation of Connecticut Filed Dec. 10, 1965, Ser.No. 512,879

7 Claims. (Cl. 165-40) ABSTRACT OF THE DISCLOSURE A tracer valveincluding a spool passage having grooves and ports which control theflow of hydraulic fluid from a power supply to motors and exhaust thefluid to a supply. A reservoir collects the hydraulic fluid and includestemperature modifying means to maintain the temperature of the fluiddischarged from the reservoir above ambient.

This invention relates to tracer valves for controlling machine tools.

Tracer valves of the class whose members include a body having aninterior spool passage with an axis, and an axially shiftable spoolwithin said spool passage are well known. Examples of these are to befound in United States Patents to Rosebrook Nos. 2,753,145 and2,835,466.

The spool and the interior wall of the spool passage customarily havegrooves and ports which control flow of pressurized hydraulic fluid froma power supply to motors, and then return the exhaust fluid to a supply.In turn, the position of the spool in the passage, which position is thesource of the primary control signal, is determined by the tilting orother displacement of a stylus which itself follows a pattern ortemplate, and serves to position the spool within the passage. The flowof fluid passed by the valve is a function of spool displacement, aswell as the peripheral length of gap around the spool. It is evidentthat changes in the physical characteristics of the valve will have aneffect on the part manufactured by the valve, and this is true both frompart to part, and from region to region of the same part.

It is an object of this invention to remove one appreciable variableelfect from tracer valves, and thereby increase their stability. Byincreasing their stability, there results an increase in the quality ofthe parts made on the machines controlled by them.

This invention comprises the combination of a tracer valve of the aboveclass, with a fluid-flow conduit in heat transfer relationship to thesaid tracer valve. A fluid supply discharges into this conduit, andmeans is provided for maintaining temperature of the fluid dischargedfrom the fluid supply above ambient.

According to a preferred but optional feature of the invention, the samefluid supply which supplies the fluidflow conduit also supplies thetracer valve, and restrictor means is provided in the said fluid-flowconduit to restrict the flow therethrough.

According to still another preferred but optional feature of theinvention, the fluid-flow conduit is provided within the body of thetracer valve.

The above and other features of this invention will be fully understoodfrom the following detailed description and the accompanying drawings inwhich:

FIG. 1 is a side elevation, partly in cutaway crosssection and partly inschematic notation, showing the presently preferred embodiment of theinvention; and

FIG. 2 is a cross-section taken principally at line 22 of FIG. 1.

FIG. 1 illustrates a tracer valve 10 according to the invention whichmay be utilized for the same types of control as those shown in UnitedStates Patents to Rosebrook,

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Nos. 2,753,145 and 2,835,466, and to Weaver, No. 3,055,- 393. Such'atracer valve customarily includes a body 11 which may comprise a jacket12 and an internal sleeve 13. The sleeve includes an internal spoolpassage 14 with an axis 15, this passage generally being cylindrical. I

Within this passage there is disposed a spool 16 having an exteriorperipheral surface 17 which matches that of the internal spool passage.This spool makes a fluid-sealing fit with the wall of passage 14 and isadapted to slide axially therein. The body also includes a cap 1 8 torestrain a bias spring 19 which bears against the top of the spool so asto bias it downwardly against a stylus 20. The stylus is mounted in asocket 21 by a ball-like member 22 which is incorporated in the lengthof the stylus. Opposed sockets 23, 24 on the spool and the end of thestylus respectively trap a ball 25 between them, and then tilting of thestylus around the center 26 of ball-like member 22 causes upwardmovement of the spool from a lower position. The lower position isassumed when the stylus is vertical in FIG. 1. The function of thissocket is fully set forth in Rosebrook Patent No. 2,753,145. Fulldetails of this portion of the device are not given here because theyare not of importance to the invention.

The wall of the internal spool passage includes motor supply grooves 27,28, which are connected through passages 29, 30, respectively, to motorsupply ports 31, 32. A pressure groove 33 and a pair of exhaust grooves34, 35 are formed in the spool. The sleeve is pierced by exhaust ports36, 37 and pressure port 38. Pressure port 38 is connected by conduit 39through pump 40 to a reservoir 41. Exhaust ports 36 and 37 are connectedto an exhaust conduit 42 which discharges to the reservoir. A passage42a joins exhaust groove 37 to exhaust conduit 42. Scavenging grooves43, 44 are connected to a vacuum line 45. The pressure port opens intothe pressure groove. The exhaust ports open into the exhaust grooves.The motor supply grooves are adapted to be overlapped by the pressureand one of the exhaust grooves when shifted from a central, symmetricalposition.

A fluid flow conduit 50 (FIG. 2) is formed peripherally between thejacket and the sleeve for the circulation of fluid to maintain a giventemperature condition in the tracer valve. It may conveniently beformed, as are some of the other grooves, by machining it in the outersurface of the sleeve which is pressed fitted into the jacket.

The flow conduit includes a supply line 51 and exhaust line 52. Thesupply line includes a restrictor 53 where it branches olf of pressureconduit 39. This restrictor prevents the flow conduit 50 from causing anexcessive drop in pressure in the principal supply line which is commonto both the fluid supply system for tracer valve operation and formaintenance of temperature.

It will be noted that FIG. 2 includes sections taken at twoelevationsone at the lower inlet level, and the other at the upperexhaust level. It has been found that one peripheral groove of this typefor circulation of temperature-controlled fluid is sufiicient to keepthe valve at a desired temperature. The groove in this case is groove 52at the upper level in FIG. 2. Alternatively, the valve could bejacketed, or a larger number of grooves of this kind could be formed atany desired elevation and at any desired number of these elevations. Ameans is thereby provided for maintaining the temperaure of the fluidsupplied to the system at any desired level. It will be noted that flowthrough much of the valve, all from the same temperature-regulatedsource, is intermittent. For example, there is flow through any of thegrooves associated with the spool only when the spool is shifted offcenter as is shown in FIG. 1. However, fluid flow through conduit 50 iscontinuous, which provides steady flow to keep the temperature stable.

In order to maintain the value at an even level, it is necessary thatthis temperature be above ambient. For this reason a heater 55, undercontrol of a thermostat 56, is Placed in the reservoir. An electricalpower supply 57 such as a battery supplies this heater attempts tomaintain a desired temperature level in fluid 58. In addition toheating, it may be necessary to cool the fluid. For this purpose aconventional radiator 59 is provided across which a fan 60 circulatescool air. A pump 61 withdraws fluid from the radiator, sending itthrough a thermostat 62 which controls the actual flow through theradiator, and returns the cooled fluid to the reservoir.

It has been found that it is best to keep the reservoir between about100 F. and 110 F., or approximately 30 F. above ambient temperature-inthe usual machine shop. The valves temperature can and should becontrolled to about :1" F. of a selected temperature. This differentialof the fluid from ambient is' above that of expectable and predictablelocal effects such as variations of temperature of the room during theday, or of transient cooling effects of the surroundings. By having asufficiently large ditferential, the local effects are overcome by thecontrol exerted by the fluid supply. It has been found that about /5.gal. per minute through fluid flow conduit 50 can effectively keep aconventional tracer valve at a consistent temperature, and therebyimprove the accuracy of its control.

This invention is not to be limited by the embodiment shown in thedrawings and described in the description which is given by way ofexample and not of limitation, but only in accordance with the scope ofthe appended claims.

I claim:

1. In combination: a tracer valve of the class which includes a stylusadapted to contact a pattern or template, a body having an interiorspool passage with an axis, and an axially shiftable spool within saidspool passage, movable in the passage as a consequence of stylus motion,the wall of the passage and the periphery of the spool being suitablygrooved and ported to control fluid flow through the valve as a functionof the motion of the stylus in response to contact with a pattern ortemplate; a fluid flow conduit in heat transfer relationship with thesaid tracer valve; a fluid supply discharging into said conduit; andmeans for maintaining the temperature of the fluid discharged from saidfluid supply above ambient thereby to maintain the tracer valvesubstantially at a predetermined temperature above ambient.

2. A combination according to claim 1 in Which the said fluid supplyalso supplies fluid to the said grooving and porting for control by thetracer valve; and in Which a restriction is placed in said fluid flowconduit to restrict the rate of fluid flow therethrough.

3. A combination according to claim 1 in which the said conduit isdisposed within the tracer valve.

4. A combination according ot claim 3 in which the said fluid supplyalso supplies fluid to the said grooving and porting for control by thetracer valve; and in which a restriction is placed in said fluid flowconduit to restrict the rate of fluid flow therethrough.

5. A combination according to claim 1 in which the means for maintainingthe temperature comprises a reservoir for fluid to be supplied; a heaterin said reservoir for heating its contents; and a thermostat meansresponsive to the temperature of said fluid and effective to control theheater.

6. A combination according to claim 1 in which the means for maintainingthe temperature comprises a reservoir for fluid to be supplied; aradiator; a pump connected to the reservoir and to the radiator; and athermostat means responsive to the temperature of said fluid andeffective to control the quantity of fluid which flows through theradiator from the reservoir through the 'pump, and returns to thereservoir.

7. A combination according to claim 6 in which the means for maintainingthe temperature additionally comprises a heater in said reservoir.

References Cited UNITED STATES PATENTS 2,293,854 8/1942 Sauzedde -5462,352,187 6/1944 Ellinwood 6054.5 2,900,995 8/1959 Dickerson et a1137-340 3,024,808 3/1962 Woodruff 91-37 X FOREIGN PATENTS 872,763 2/1942France.

EDWARD 1. MICHAEL, Primary Examiner.

ROBERT A. OLEARY, Examiner.

M. A. ANTONAKAS, Assistant Examiner.

